Control system for prosthetic devices

ABSTRACT

A control system and method for prosthetic devices is provided. The control system comprises a transducer for receiving movement from a body part for generating a sensing signal associated with that movement. The sensing signal is processed by a linearizer for linearizing the sensing signal to be a linear function of the magnitude of the distance moved by the body part. The linearized sensing signal is normalized to be a function of the entire range of body part movement from the no-shrug position of the moveable body part through the full-shrug position of the moveable body part. The normalized signal is divided into a plurality of discrete command signals. The discrete command signals are used by typical converter devices which are in operational association with the prosthetic device. The converter device uses the discrete command signals for driving the moveable portions of the prosthetic device and its sub-prosthesis. The method for controlling a prosthetic device associated with the present invention comprises the steps of receiving the movement from the body part, generating a sensing signal in association with the movement of the body part, linearizing the sensing signal to be a linear function of the magnitude of the distance moved by the body part, normalizing the linear signal to be a function of the entire range of the body part movement, dividing the normalized signal into a plurality of discrete command signals, and implementing the plurality of discrete command signals for driving the respective moveable prosthesis device and its sub-prosthesis.

This is a division of application Ser. No. 07/937.325, filed Aug. 31,1992, now U.S. Pat. No. 5,376,128.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control system and associated methodfor use with prosthetic devices. Particularly, the present inventionrelates to a prostheses control system and method for below-the-elbowamputees.

2. Description of the Prior Art

Typically, a prostheses aims to give relief to persons disabled by theabsence or defect in their body parts. The field of prostheses has mostadvanced in the area of artificial arms and artificial legs. Inparticular, artificial arms are required to produce complicated motions.A high degree of perfection has been reached with respect to the use ofelectric motors and hydraulic drives for operating such artificial armsand legs. The control of a drive mechanism in association with aprosthesis calls for highly complicated processing. Various methods havepreviously been used and proposed for the purpose of such control.

Much work has been done in the field of prosthetic devices. Prior artdevices include the hook and cable system developed in the 1800's andstill used today. Hydraulic actuated prostheses and computer controlled"bionic" type devices are available. The disadvantages of prior devicesrange from only two digit ("hook") control, to lack of wrist control andhigh frictional forces associated with the cable and hook hardwareresulting in extreme complexity, to burdensome maintenance, toquestionable reliability, and to exorbitant cost associated with bionicmethodology.

Unfortunately, the prior methods and apparatus used in association withthe control of prostheses tend to have the common disadvantage that thecontrol devices are unproportionately large in size for the number ofmodes of motion the artificial limb is expected to produce. Similarly,numerous methods have been proposed for the discrimination of controlsignals used for causing artificial limbs to produce various motions.Such methods and apparatus have, for example, used a plurality ofindependent input devices, prescribed voice sounds uttered by the useras instruction signals, bioelectric signals for controlling the motion,feedback circuits for controlling the motion, complicated models,mini-central processing units, varying a cutoff frequency, the use ofmechanical structures such as springs and associated stepping motors tosimulate finger and wrist motion, and related pressure devices to assistin controlling prostheses.

It is known that most prosthetic limb devices are clumsy, have severemotion limitations, and are unnatural in appearance. Nonetheless, remotemanipulators bearing similarities to the forearm and hand have been usedin space, planetary exploration, deep-sea work and nuclear research.Most such devices suffer from a high cost, lack of controllability andan inability to reproduce human limb motions. Most remote manipulatorsof the foregoing types, including the prosthetic devices are unable toperform typical motions without including significant equipment.Developers have approached the problem along two separate fronts. First,the typical approach is not to use wrist motion at all. Such an approachcan be recognized by the use of a claw or hook-type prosthetic. The clawor hook must be rotated about an axis of the arm to align the claw orhook with the object to be grasped. Typically, the prior motion must befollowed by orienting the arm such that the object picked up can be heldat an acceptable angle relative to vertical. Second, when wrist motionis necessary and the size, weight and cost are not constraints, agimbaled, azimuth/elevation-type wrist joint has been used. A two degreeof freedom gimbaled wrist manipulator can duplicate the total wristmotion. Even then, with a two degree of freedom gimbaled arrangement,the required placement of drive motors and control devices for this typeof manipulator results in a rather large and bulky package.

Artificial limbs are readily attached to a shoulder socket or upper arm.Typically the most favored prosthesis is one which uses the "shrug"control. A shrug-type controller typically includes a hook and cablesystem which was originally developed in the 1800's. Such systems haveonly two digit control, lack wrist control and have high frictionalforces with respect to the cable and hook hardware. Further, suchhardware is complex, difficult to maintain, not reliable and expensive.Nonetheless, the hook and cable, shrug control method is still widelyfavored by below the elbow amputees. Reasons cited for the widelyfavored acceptance of shrug control devices include the low cost, theease of repair, the reliability and the simple pretension of the hookderived from the shoulder/back muscle through a harness and cableassembly.

Typically, such prosthesis have a shoulder socket placed on the shoulderstump comprising an elbow joint operated by rods and connected to theshoulder socket, a forearm socket pivotally attached to an elbow jointand provided means for rotating the forearm, and an artificial handcomplete with moveable fingers united with the forearm socket. Movementsof the arm at the elbow joint and the opening and closing of the fingersare carried out with respect to such prosthesis by the aid of themovement of the rods.

Obviously, movement by means of such artificial limbs requires greateffort by the wearer of the arm. These efforts are particularly greatwhen opening and closing the fingers of an artificial hand. Further, thepossibility of making these movements restricted as they are can beperformed only in a number of certain positions of the stump(prosthesis). The process of transmitting these efforts from theshoulder and other parts of the body by the aid of rods is veryuncomfortable and requires complex and unsightly movements.

Although many prosthetic devices have been developed, one system widelyfavored by below-the-elbow amputees is a variation of the "hook andcable system." Reasons for the preferred use of the hook and cablesystem, cited by experts in this field include low costs, easy repair,reliability, and simple pretension of the hook derived from theshoulder/back muscle through the harness cable assembly.

The advantages of the present invention over the prior devices include:the easy to use "shrug" techniques to generate discrete finger digitcontrol and wrist rotation; the compactness with which the controlsystem can be easily mounted in the body of the prosthetic device;conformal printed circuit type conductors can be employed; improvedmaintenance; individual finger digit control is proposed instead of hookwith cable actuation; wrist rotation capability; hardware programmable;lower cost than conventional prostheses and the use of frictional forcesfor actuation.

The present invention facilitates easy adaptation by either child oradult users, compensating for the "shrug" distance adjustable by thepotentiometer. The "shrug" control envelope may be linear or logarithmicas determined by the integrated circuit selection. The electroniccontrol package of the present invention is quite small in comparison tothe prior devices. The electronic control package of the presentinvention is easily mounted in the prosthetic device and requires noadditional containers or carriers to be worn by the user.

Primary to the present invention is the combination of the well knownconcept of control of prosthetic devices to the application ofprosthetic arms. This combination results in improved finger and wristcontrol of the prostheses using a bar graph driver for simple,inexpensive generation of discrete control signals for discriminatingand calibrating signals to establish multiple control routines.

It is, therefore, a feature of the present invention to provide aprosthesis control system and method which in normal use provides forsequential or specific control of each finger digit, for wrist rotationor the like from signals derived from a transducer actuated byshoulder/back muscle movement.

A feature of the present invention is to provide the user with a "shrug"technique apparatus and method to generate discrete digit and wristmovement.

Another feature of the present invention is to provide a control systemthat can be easily mounted in the body of the prosthetic device.

Yet another feature of the present invention is to provide novel sensingand electronic control techniques.

Still another feature of the present invention is to provide a highlevel signal using typical shrug techniques.

Still another feature of the present invention is to provide individualfinger digit control with a "shrug" techniques as opposed to a "hook"with cable actuation.

Still another feature of the present invention is to provide forindividual finger digit control at the same time as wrist rotationcapability.

Still another feature of the present invention is to provide hardwareprogrammable prostheses.

Still another feature of the present invention is to provide a low costprosthesis control system.

Still another feature of the present invention is to provide lowfrictional forces for actuation of the prosthesis control system.

Additional features and advantages of the invention will be set forth inpart in the description which follows, and in part will become apparentfrom the description, or may be learned by practice of the invention.The features and advantages of the invention may be realized by means ofthe combinations and steps particularly pointed out in the appendedclaims.

STATEMENT OF THE INVENTION

To achieve the foregoing objects, features and advantages and inaccordance with the purpose of the invention as embodied and broadlydescribed herein, a control system for use with a prosthetic device isprovided. The prosthetic device comprises a plurality of moveablesub-prostheses and incorporates an implementation of the well knownharness-and-shoulder control hardware such that the conventionalshoulder shrug control movement associated with a moveable body partranging from the no-shrug position of the moveable body part through thefull-shrug position of the moveable body part provides control by theuser to the prosthetic device. The control system comprises (a) atransducer for receiving the movement from the body part and forgenerating a sensing signal in association with the movement of the bodypart, (b) a linearizer for linearizing the sensing signal received fromthe transducer to be a linear function of the magnitude of the distancemoved by the body part, (c) a normalizer for normalizing the linearsignal received from the linearizer to be a function of the entire rangeof body part movement from the no-shrug position of the moveable bodypart through the full-shrug position of the moveable body part, (d) adiscriminator for dividing the normalized signal received from thenormalizer into a plurality of discrete command signals, and (e) aconverter connected to the prosthetic device for receiving the discretecommand signals and driving the respective moveable sub-prostheses ofthe prosthetic device. Further, the present invention provides that thediscrete command signals may be sustained linear commands, unsustainedlinear commands, sustained logarithmic commands or unsustainedlogarithmic commands. Still further, the respective logarithmic commandscan be sequential or non-sequential, and similarly, the linear commandscan be sequential or non-sequential.

In another embodiment of the present invention, a control system for usewith a prosthetic device is provided. The prosthetic device comprises aplurality of moveable sub-prostheses and incorporates an implementationof the well known harness-and-shoulder control hardware such that theconventional shoulder shrug control movement associated with themoveable body part ranging from the no-shrug position of the moveablebody part through the full-shrug position of the moveable body partprovides control by the user to the prosthetic devices. Wherein thecontrol system comprises (a) a shoulder harness for engaging the bodypart and for receiving and modifying the movement from the body part,(b) a linear potentiometer for receiving the movement from the shoulderharness and for generating a linear sensing signal in consonance withthe movement of the body part, (c) an attenuator potentiometer forreceiving the linear signal from the linear potentiometer and forscaling the linear signal to be a function of the entire range of bodypart movement from the no-shrug position of the moveable body partthrough the full-shrug position of the moveable body part, (d) a bargraph driver for receiving the scaled linear signal from the attenuatorpotentiometer and for dividing the scaled signal into a plurality ofdiscrete command signals, (e) a current driver for receiving thediscrete command signals from the bar graph driver and for generatingdrive signals, and (f) a solenoid/motor arrangement in operationalassociation with the prosthetic device for receiving the drive signalsfrom the current driver and controlling the respective moveablesub-prostheses of the prosthetic device.

In yet another embodiment of the present invention a method is providedfor controlling a prosthetic device. The method of controlling theprosthetic device is associated with a prosthetic device comprising aplurality of moveable sub-prostheses in association with animplementation of the well known harness and shoulder control hardwaresuch that the conventional shoulder shrug control movement associatedwith a moveable body part ranging from the no-shrug position of themoveable body part through the full-shrug position of the moveable bodypart provides control by the user to the prosthetic device. The methodfor controlling this prosthetic device comprises the steps of receivingthe movement from the body part, generating a sensing signal inconsonance with the movement of the body part, linearizing the sensingsignal to be a linear function of the magnitude of the distance moved bythe body part, normalizing the linear signal to be a function of theentire range of body movement from the no-shrug position of the moveablebody part through the full-shrug position of the moveable body part,dividing the normalized signal into a plurality of discrete commandsignals, and implementing the plurality of discrete command signals fordriving the respective moveable sub-prostheses of the prosthetic device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings which are incorporated in and constitute apart of the specification, illustrate a preferred embodiment of theinvention and together with the general description of the inventiongiven above and the detailed description of the preferred embodimentgiven below, serve to explain the principles of the invention.

FIG. 1 is a flow diagram illustrating one embodiment of the controlsystem for prosthetic devices of the present invention;

FIG. 2 is a flow diagram of another embodiment of the control system forprosthetic devices of the present invention;

FIG. 3 is a detailed schematic of one embodiment of the presentinvention illustrating a control system for prosthetic devices;

FIG. 4 is a schematic view of a preferred embodiment of the controlsystem for prosthetic devices associated with the present invention; and

FIG. 5 is a drawing illustrating the versatility of the presentinvention with respect to individual users.

The above general description and the following detailed description aremerely illustrative of the generic invention, and additional modes,advantages, and particulars of this invention will be readily suggestedto those skilled in the art without departing from the spirit and scopeof the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present preferredembodiments of the invention as described in the accompanying drawings.

FIG. 1 is a schematic of a preferred embodiment of the present inventionillustrating a control system for prosthetic devices. The prostheticdevice utilized with the present invention has a plurality of moveablesub-prostheses. The prosthetic device, and its plurality of moveablesub-prostheses, incorporates the implementation of the well knownharness-and-shoulder control hardware. The well knownharness-and-shoulder control hardware provides that the conventionalshoulder shrug control movement associated with a moveable body pan canbe used. The moveability of the body part ranges from a no-shrugposition through a full-shrug position. The relative movement of theuser's body part provides control for the user to the prosthetic device.

The control system of the present invention, illustrated in FIG. 1,comprises generally a sensor/transducer 104, a linearizer 106, anormalizer 108, a discriminator 110, a converter 112 in operativeassociation with the moveable body part 102 and the prosthesis 114. Thesensor/transducer 104 engages the moveable body part 102. The transducer104 generates a sensing signal operatively associated with the movementof the body part 102. The sensing signal generated by the transducer 104is applied to the linearizer 106. The linearizer 106 linearizes thesensing signal to create a linear function of the magnitude of thedistance moved by the body part 102. The linearized signal from thelinearizer 106 is provided to the normalizer 108. The normalizer 108normalizes the linear signal to be a function of the entire range ofbody part 102 movement from a no-shrug position through the full-shrugposition of the individual user. The normalized signal created by thenormalizer 108 is provided to the discriminator 110. The discriminator110 divides the normalized signal into a plurality of discrete commandsignals. The discrete command signals created by the discriminator 110are provided to the converter 112. The converter 112 is in operationalassociation with the prosthetic device 114. The converter 112 receivesthe discrete command signals from the discriminator 112 and uses thesignals for driving the respective moveable sub-prostheses 114 of theprosthetic device.

FIG. 2 is a flow diagram illustrating another embodiment of the controlsystem for prosthetic devices associated with the present invention. Theprimary elements of the embodiment of the control system illustrated inFIG. 2 are a shoulder harness 102, a linear potentiometer 204, anattenuator potentiometer 206, a bar graph driver 208, a current driver210, a solenoid/motor arrangement 212 and a prosthesis 214. As with theprior embodiment, the prosthetic device has a plurality ofsub-prostheses. Further, the prosthetic device incorporates animplementation of the well known harness-and-shoulder control hardwaresuch that the conventional shoulder shrug control movement associatedwith a moveable body part can range from the no-shrug position to thefull-shrug position of the moveable body part. The movement of the bodypart provides control by the user to the prosthetic device 214. Thecontrol system illustrated in FIG. 2 comprises the shoulder harness 202for directly engaging the moveable body part and for receiving themovement there from. The body movement from the shoulder harness 202 isapplied to the linear potentiometer 204. The linear potentiometer 204generates a linear sensing signal in consonance with the movement of theshoulder harness 202. The linear sensing signal of the potentiometer 204is applied to the attenuator potentiometer 206. The attenuatorpotentiometer 206 scales the linear sensing signal. Preferably, thescaling applied by the attenuator potentiometer 206 provides a functionof the entire range of body part movement from the no-shrug position ofthe moveable body part to the full-shrug position of the moveable bodypart. The scaled linear signal from the attenuator potentiometer 206 isapplied to the bar graph driver 208. The bar graph driver 208 dividesthe scaled signal into a plurality of discrete command signals. Thediscrete command signals are used by the current driver 210 forgenerating drive signals. The drive signals generated by the currentdriver 210 are applied to the solenoid or motor arrangement 212. Themotor arrangement 212 is in operational association with the prostheticdevice 214. The prosthetic device receives the drive signals from themotor arrangement 212 as provided by the current driver 210.

FIG. 3 illustrates a more detailed version of yet another embodiment ofthe present invention. FIG. 3 is quite similar to FIG. 1, but includesmore specificity with respect to variations on acquiring an appropriatesignal for a prosthesis 358 in association with a moveable body part302. A moveable body part 302 provides motion which is detected by atransistor 304. The sensor/transducer 304 provides an analog signal 306.The analog signal 306 is provided via a line 308 to a linearizer 310.The linearizer 310 creates a linear sensing signal 312. The linearsensing signal 312 is provided via a line 314 to a normalizer 316. Thenormalizer 316 provides a normalized signal 318. The normalized signal318 is provided via a line 320 to a discriminator 322. The discriminator322 generates specific command signals 324. The command signals 324 areprovided via a line 326 to a converter 328. The converter provides fourdistinct options: the command signals can be sustained linear commands330, sustained logarithmic commands 332, unsustained linear commands 334or unsustained logarithmic commands 336. The sustained linear commands330 can be sequential commands 338 or non-sequential commands 342. Thesustained logarithmic commands 332 can be sequential commands 340 ornon-sequential commands 346. Similarly, the unsustained linear commands334 can be sequential commands 344 or non-sequential commands 350. Andlastly, the unsustained logarithmic commands 336 can be eithersequential commands 348 or non-sequential commands 352. The respectivecommands are provided to an electromechanical device 356 in associationwith a drive signal 354. The electromechanical device 356 is inoperational association with the prosthesis 358.

FIG. 4 illustrates a schematic view of one embodiment of the controlsystem for prosthetic devices of the present invention. The inventionillustrated in FIG. 4 also employees the favored harness-and-shouldershrug control. It should be noted that the shoulder hardware does notinclude mechanical portions as does prior used devices. A shoulderharness 402 incorporates a powered linear potentiometer 404. The linearpotentiometer 404 generates a linear electrical signal in workingrelationship with the conventional shoulder shrug control movement. Thelinear signal is provided to an attenuator potentiometer 406. Theattenuator potentiometer 406 facilitates the scaling of shoulderphysical movement with the electrical sensing signal. The scalingaccommodates various users. For example, children or elderly personswith less shoulder shrug capability can function just as easily as userswith great flexibility in shoulder shrug capability. Thus, for example,some individuals might only be able to create a one inch "shrug" whereasother users might be able to force a three inch "shrug." The attenuatorpotentiometer 406 is adjusted to a desired electrical output, forexample, one volt for a full shrug. An analog signal is created and fedto a bar graph driver 408 which receives electrical power from battery410. The bar graph driver 408 converts the analog input signal from azero shrug to a full shrug via a plurality of discrete sustainedsequential linear commands. For example, ten discrete commands might beappropriate. Alternately, the bar graph driver 408 can convert theanalog input signal to a plurality of sustained sequential logarithmicdigital commands. Yet still another alternative for use with the bargraph driver 408 is to provide a "dot" mode of operation of the bargraph driver. Thus, discrete nonsustained digital commands can also begenerated. By cascading two bar graph drivers, outputs comprising twentydiscrete command signals may be obtained. It is obvious to one skilledin the art that additional cascading is possible.

Each of the outputs from the ports of the bar graph driver 408 are fedinto a current driver 414 via a different respective one of a groupsinking current limiting resisters of a plurality of sinking currentlimiting resister 412. The current driver 414 drives a solenoid or otherarrangement 416. The arrangement 416 results in finger movement in, forexample, a sequential manner such that with a no shrug, all fingerswould be in the extended position. As the "shrug" begins, the thumb andfingers would move sequentially to the closed position. All of thediscrete commands may not be required. See, for example, FIG. 5. Asanother example, the "shrug" transducer may be located on the rightshoulder for finger digit control and a duplicate system can be mountedon the left shoulder for providing wrist rotation control The wristrotation control can be adapted by using a stepping motor located at thewrist which incorporates a plurality of steps received via the bar graphdriver 408. Yet still another preferred embodiment of the presentinvention provides that one or more of the digital commands, or otherselected steps equating to a full "shrug" could be used as a "home" orreset command. Thus, simultaneously, all the fingers will return to aspecific configuration. Therefore, fingers which may have been"shrugged" to a gripping position would move back to the extendedposition when the home or reset command is engaged.

It is appreciated by those skilled in the art that the control system ofthe present invention can be used on any device requiting signaltranslation, analog or otherwise. The analog signal translation canencompass either linear or logarithmic discrete commands, andprogressive commands, and include homing capabilities. Further, anaudible tone can be generated by each discrete command to providefurther feedback for finger or wrist positions via, for example,earphone feedback.

FIG. 5 illustrates the control signals associated with a digit and wristcontrol mechanism. The respective diode matrix can be directlyprogrammed by the user. The output signals from the bar graph driver areprovided on the abscissa and the digits and gripping information areprovided along the ordinate.

A method for controlling a prosthetic device is also provided inassociation with the present invention. The method for controlling theprosthetic device comprises the steps of receiving the movement from thebody part, generating a sensing signal in consonance with the movementof the body part, linearizing the sensing signal to be a linear functionof the magnitude of the distance moved by the body part, normalizing thelinear system to be a function of the entire range of body part movementfrom the no-shrug position of the moveable body part through thefull-shrug position of the moveable body part, dividing the normalizedsignal into a plurality of discrete command signals, and implementingthe plurality of discrete command signals for driving the respectivemoveable sub-prostheses of the prosthetic device.

Additional advantages and modification will readily occur to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus, and theillustrative examples shown and described herein. Accordingly, thedepartures may be made from the details without departing from thespirit or scope of the disclosed general inventive concept.

What is claimed is:
 1. A control system for use with a prostheticdevice, the prosthetic device comprising a plurality of moveablesub-prostheses and incorporating any implementation of harness andshoulder control hardware such that the shoulder shrug control movementassociated with a moveable body part ranging from the no-shrug positionof the moveable body part through the full-shrug position of themoveable body part provides control by the user to the prostheticdevice, the control system comprising:(a) a shoulder harness forengaging the body part and for receiving the movement from the bodypart, (b) a linear potentiometer for mechanically receiving the movementfrom said shoulder harness and for generating a linear sensing signal inconsonance with the movement of the body part, (c) an attenuatorpotentiometer for receiving the linear sensing signal from said linearpotentiometer and for scaling the linear sensing signal to be a functionof the entire range of body part movement from the no-shrug position ofthe moveable body part through the full-shrug position of the moveablebody part, (d) a bar graph driver circuit for receiving the scaledlinear signal from said attenuator potentiometer and for dividing thescaled signal into a plurality of discrete command signals, (e) currentdriver means operatively associated with said bar graph driver circuitfor receiving the discrete command signals from said bar graph drivercircuit and for generating electrical drive signals, corresponding tosaid command signals, and (f) a solenoid/motor arrangement for receivingthe drive signals from said current driver means and controlling each ofsaid moveable sub-prosthesis of the prosthetic device by a different oneof said drive signals.
 2. A control system as set forth in claim 1,wherein said attenuator potentiometer includes means for adjusting thescaling of said linear sensing signals to accommodate different rangesof shrug movement by different users of the prosthetic device.
 3. Acontrol system as set forth in claim 1 further including programmablemeans for controlling the application of said drive signals to themoveable sub-prostheses of the prosthetic device in selected sequence.